An ocular zoom optical system has been known that is employed for optical instruments, such as a telescope and binoculars, and has a configuration including a movable lens group having a negative refractive power, an intervening field stop, a movable lens group having a positive refractive power, and a fixed lens group having a positive refractive power, in order from the object side, thereby achieving zooming. For example, ocular zoom optical systems of such a type have been known that are a system with a zoom ratio of three and an apparent field of view of at least 40°, and a system with a zoom ratio of two and an apparent field of view of at least 500 (for example, see Patent Literature 1).